Detection of live/dead Xanthomonas fragariae by PCR

What is it about?

Interpretation of positive results from a PCR test is particularly challenging given the inability of PCR to differentiate between live or dead organisms. The purpose of this study was to optimise polymerase chain reaction (PCR) detection of DNA from viable Xanthomonas fragariae by using DNA intercalating dyes. A reproducible PCR protocol has been optimised to enable rapid detection of viable bacterial cells in strawberry tissue. The use of PEMAX™ at 100 μM resulted in complete inhibition of PCR amplification of dead X. fragariae cells on strawberry tissue. Repeatability and reproducibility was confirmed through inter-laboratory testing of blind panel samples.

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Why is it important?

Making a phytosanitary decision based on a positive result from a PCR test is particularly challenging given the inability of PCR to differentiate between live or dead organisms. Imported fresh produce, nursery stock or seeds/grain products that have undergone phytosanitary treatments have significant potential to generate “false positive” PCR test results by the detection of dead cells. This test could help with timely decision making at the border when X. fragariae is detected on imported fresh strawberry consignments by PCR.